Semiconductor devices are commonly found in modern electronic products. Semiconductor devices vary in the number and density of electrical components. Discrete semiconductor devices generally contain one type of electrical component, e.g., light emitting diode (LED), small signal transistor, resistor, capacitor, inductor, and power metal oxide semiconductor field effect transistor (MOSFET). Integrated semiconductor devices typically contain hundreds to millions of electrical components. Examples of integrated semiconductor devices include microcontrollers, microprocessors, charged-coupled devices (CCDs), solar cells, and digital micro-mirror devices (DMDs).
Semiconductor devices perform a wide range of functions such as signal processing, high-speed calculations, transmitting and receiving electromagnetic signals, controlling electronic devices, transforming sunlight to electricity, and creating visual projections for television displays. Semiconductor devices are found in the fields of entertainment, communications, power conversion, networks, computers, and consumer products. Semiconductor devices are also found in military applications, aviation, automotive, industrial controllers, and office equipment.
Semiconductor devices exploit the electrical properties of semiconductor materials. The atomic structure of semiconductor material allows its electrical conductivity to be manipulated by the application of an electric field or base current or through the process of doping. Doping introduces impurities into the semiconductor material to manipulate and control the conductivity of the semiconductor device.
A semiconductor device contains active and passive electrical structures. Active structures, including bipolar and field effect transistors, control the flow of electrical current. By varying levels of doping and application of an electric field or base current, the transistor either promotes or restricts the flow of electrical current. Passive structures, including resistors, capacitors, and inductors, create a relationship between voltage and current necessary to perform a variety of electrical functions. The passive and active structures are electrically connected to form circuits, which enable the semiconductor device to perform high-speed calculations and other useful functions.
Semiconductor devices are generally manufactured using two complex manufacturing processes, i.e., front-end manufacturing, and back-end manufacturing, each involving potentially hundreds of steps. Front-end manufacturing involves the formation of a plurality of die on the surface of a semiconductor wafer. Each semiconductor die is typically identical and contains circuits formed by electrically connecting active and passive components. Back-end manufacturing involves singulating individual semiconductor die from the finished wafer and packaging the die to provide structural support and environmental isolation. The term “semiconductor die” as used herein refers to both the singular and plural form of the words, and accordingly can refer to both a single semiconductor device and multiple semiconductor devices.
One goal of semiconductor manufacturing is to produce smaller semiconductor devices. Smaller devices typically consume less power, have higher performance, and can be produced more efficiently. In addition, smaller semiconductor devices have a smaller footprint, which is desirable for smaller end products. A smaller semiconductor die size can be achieved by improvements in the front-end process resulting in semiconductor die with smaller, higher density active and passive components. Back-end processes may result in semiconductor device packages with a smaller footprint by improvements in electrical interconnection and packaging materials.
FIG. 1a shows a substrate 10 with conductive traces 12, 14, and 16 formed on a surface of the substrate. Conductive trace 16 includes a wider interconnect site 18. In FIG. 1b, a photoresist layer 20 is formed over the surface of substrate 10 and conductive traces 12-16. A portion of photoresist layer 20 is removed to expose interconnect site 18. Semiconductor die 22 has a contact pad 24 formed over an active surface of the semiconductor die. A bump 26 is formed over contact pad 24. Semiconductor die 22 is mounted to substrate 10 with bump 26 metallurgically and electrically connected to interconnect site 18.
FIG. 2a shows a substrate 30 with conductive traces 32, 34, and 36 formed on a surface of the substrate. Conductive trace 36 includes a wider, circular interconnect site 38. In FIG. 2b, a photoresist layer 40 is formed over the surface of substrate 30 and conductive traces 32-36. A portion of photoresist layer 40 is removed to expose interconnect site 38. Semiconductor die 42 has a contact pad 44 formed over an active surface of the semiconductor die. A bump 46 is formed over contact pad 44. Semiconductor die 42 is mounted to substrate 30 with bump 46 metallurgically and electrically connected to interconnect site 38.
In each case, the interconnection between the bump and interconnect site is susceptible to interconnect voids, shown in FIG. 2b as void 48. The voids reduce the interconnect reliability and can cause manufacturing defects and latent defects.